Excessive postoperative blood loss which might amount to more than 2 L per 24 hours or more than 200 mL per hour is a known complication of cardiac surgery. Reoperation/re-exploration for bleeding is a strong independent risk factor for adverse outcome following cardiac surgery with higher mortality and morbidity rates. In addition, postoperative bleeding requiring multiple transfusions and surgical re-exploration is associated with higher costs, increased sternal wound infection, and transfusion-related infection.
To evacuate blood from the pericardial cavity—and if necessary pleural cavities,—chest tubes are left postoperative. However, when blood loss is excessive or when clots start to develop more rapidly, the drains often fail in their function to evacuate all accumulated blood. Stasis of clots and blood in the pericardial (and/or pleural) cavity may lead to high fibrinolytic activity, maintenance of blood loss and in some cases to cardiac tamponade. In case of acute cardiac tamponade the pressure in the pericardial space exceeds the filling pressure of the heart, leading to collapse of the thinwalled right atrium and consequently to inflow obstruction of blood towards the heart. This will lead to low cardiac output and if not detected and treated early eventually to death. In case of cardiac tamponade only emergency reoperation can save the patient although even in this group mortality and morbidity rates are higher. This specially applies to delayed reoperation, indicating that early detection is essential.
In current clinical practice there are no special measures to prevent cardiac tamponade other than leaving the normal pericardial/wound drains and be very alert for cardiac tamponade to occur. The monitoring that is used is blood pressure and central venous pressure (CVP). When a blood pressure drop is observed it is actually too late because the tamponade is already there and the patient will probably not be stable enough to return to the OR. Central venous pressure is measured in the right atrium and is a reflection of the intrapericardial pressure because the right atrium is very thin walled. But it is indirect and often not reliable because it depends on the patient's position, the transducer position and often the line is used for infusion of medication. So a continuously measured intrapericardial pressure would be a great improvement of the patient's safety.
The clinical significance of cardiac tamponade and early detection and timely re-intervention for bleeding is discussed by Haneya A et al. Re-Exploration for Bleeding or Tamponade after Cardiac Surgery: Impact of Timing and Indication on Outcome. Thorac Cardiovasc Surg. 2014 Sep. 29. The citations below are illustrative for the serious consequences of an acute cardiac tamponade.
“Objectives: Re-exploration after cardiac surgery remains a frequent complication with adverse outcomes. The aim of this study was to evaluate the impact of timing and indication of re-exploration on outcome.
Methods: A retrospective, observational study on a cohort of 209 patients, who underwent re-exploration after cardiac surgery between January 2005 and December 2011, was performed. The cohort was matched for age, gender, and procedure with patients who were not re-explored during the same period.
Results: The intraoperative and postoperative transfusion requirements were higher in the re-exploration group (p<0.01). Patients in the re-exploration group had significantly higher incidences of postoperative acute renal injury (10.0 vs. 3.3%), sternal wound (9.1 vs. 2.4%) and pulmonary (13.4 vs. 4.3%) infections, longer ventilation time (22 [range, 14-52] vs. 12 [range, 9-16] hours) and intensive care unit stay (5 [range, 3-7] vs. 2 [range, 2-4] days), and higher mortality rate (9.6 vs. 3.3%). However, the multivariate logistic regression analysis demonstrated that not the re-exploration itself, but the deleterious effects of re-exploration (blood loss and transfusion requirement) were independent risk factors for mortality. Mortality was 5.3% for patients who were re-explored within the first 12 hours and 20.3% for patients who were re-explored after 12 hours (p=0.003). Mortality was 3.6% for patients with bleeding and 31.4% for patients with cardiac tamponade for indication of re-exploration (p<0.001).
Conclusions: This study indicates that re-exploration after cardiac surgery is associated with increased mortality and morbidity. Patients with delayed re-exploration and suffering from cardiac tamponade have adverse outcome.”
It is an object of the invention to provide a system and/or method that reduces one or more of the above risks or complications, in particular caused by post-operative blood loss from the pericardial cavity, and to prevent or at least provide an early detection of an increased threat of acute cardiac tamponade This is achieved by a flushing system as defined in claim 1 which is based on a unique combination of sensors each providing signals to a control unit which controls the flow rate of the infusion liquid to the pericardial cavity in a patient.
Flushing systems for flushing various body cavities during and/or an operation are known in the art. The flushing or irrigation of body cavities was introduced as a necessity during endoscopic surgery (e.g. hysterectomy or operations on the bladder) in order to ensure the surgeon's clear view of the operation site ,but also to remove collected particles of tissue, blood and fragments form the interior of the body cavity. This made “fluid management” of the irrigation fluid during operations an obvious desideratum, both for the securing a continuous flow of irrigation fluid and for quantifying the blood loss during the operation
Thus, WO 02/07798 A2 describes a system for securing continuous flow during an operation. The system is mainly concerned with urological endoscopic operations where large volumes of fluid are necessary to continuously flush the operation site in order to maintain visibility during the operation and post-operational flushing of the operated body cavity is desired. The system has a plurality of containers and sensors and closure devices to ensure a switch from an empty to a full container and means for measuring the volume of fluid from the operation site and compare the fluid delivered with fluid removed during and after the operation e.g by use of suitable volume sensors This balance of fluids is necessary because of a special problem related to endoscopic operations, viz. the risk of absorption of flushing liquid in the patient's body. An opacity meter may be used to measure the clarity of the fluids removed, so as to determine whether there is still bleeding. Also, such a system cannot be used to meet the special requirements relating to post-operational pericardial flushing with risk of provoking a cardiac tamponade.
The pericardial flushing device is specifically designed to clean the pericardial space after cardiac surgery. The system works by flushing the pericardial cavity with a saline (or other) solution, thereby lowering the viscosity and the hematocrit value of the blood present in the cavity and at the same time preventing the formation of larger clots. Cleaning the pericardial space by flushing will prevent clogging of the chest drains and the consequent accumulation of blood and clots in the pericardial space. This will lead to less postoperative bleeding and diminish the risk for provoking an acute cardiac tamponade. According to the invention, this is achieved by means of unique use of volume, hematocrit and pressure sensors in the flushing system as further described below.
When the outflow drains clog partially or completely despite the flushing device, the infused liquid volume is added to the accumulating blood in the pericardium which will lead to a more rapid increase of the liquid volume and pressure in that particular space. Also for this reason early detection of (increased threat of) cardiac tamponade by means of a pressure sensor is essential so that a signal can be given to a control unit that the infusion of liquid should be stopped immediately.
Also, by diluting the pericardial blood effusion with saline (or other solutions), the exact amount of blood loss is unclear. Knowing exact amount of blood loss is essential in postoperative decision-making with as regards to the needs for reoperation/re-exploration of the pericardial space. In table 5-6 the criteria for reoperation are given (from Cardiac Surgery textbook by John W. Kirklin and Brian G. Barratt-Boyes, second edtion 1993).
TABLE 5-6ENERAL CONSIDERATIONSChest Drainage Criteria for ReoperationChest Drainage Indicating ReoperationHourly Amount Total Preoperative(ml · h−1)Amount (ml)WeightNo. of Successive HoursaHour No.b(kg)123455.07060501201306.07060501301557.07060501501808.09070501752009.090806019523010.0100906522026012.01301008026030014.01501209030036016.017014010035040018.019515012039046020.020017513045052025.027022016054065030.032526019565077035.038030023076090040.04303502608001,03545.05004003009751,15050.05004003001,0001,200aReoperation is advisable if the patient has bled the amount indicated in any 1 hour (column 1), the lesser amount in column 2 during each of any 2 successive hours, or the still smaller amount (column 3) in each of any 3 successive hours.bReoperation is advisable, if by the end of the fourth or fifth postoperative hour, the patient has bled in total the amount indicated.
The criteria for patients of 50 kg apply for all adult patients with a body weight of more than 50 kg. From the table one can derive that in the decision-making process not only the absolute amount of blood loss, but also the trend is important. A relatively high amount of blood loss can still be acceptable as long as the trend is downwards.
Following from this, it is important to know the exact amount of blood loss per hour, the trend in blood loss and the total amount of blood loss over the whole postoperative period. This will enable the medical staff to to make a well-founded and timely decision whether or not to take the patient back to the operation room for re-exploration of the wound area.
This will also contribute to the clinical decision whether or not to give a blood transfusion. This in itself will also affect the patients' outcome. Not giving a blood transfusion when necessary will worsen the outcome and on the other side, giving a blood transfusion when not really necessary will do the same.
Transfusing an anaemic patient will improve the outcome. Blood transfusion has a clearly defined role in the management of haemorrhagic shock and is presumably beneficial in situations where a critically low hematocrit is contributing to a state of oxygen-supply dependency. A number of studies have demonstrated that low hemoglobin (Hb) concentrations and decreased oxygen delivery increase mortality. Thus it was found that patients who had a lower hematocrit during surgery were associated with a higher risk of in-hospital mortality. The potential benefits are, however, countered by many transfusion-associated complications: the risk of transfusion-associated lung injury, transfusion associated immunomodulation, transfusion-related circulatory overload,) and cellular hypoxia. Blood transfusions have also been linked to postoperative renal dysfunction, pneumonia, wound infections) and severe sepsis.) There have been several recent well-designed randomized control trials in patients undergoing cardiac surgery showing a significant association of transfusion with increased short- and long-term postoperative mortality of 66%; morbidity and healthcare costs.